You may want to check the permissions in Amazing Charts folder on the server. I had same problem, program not able to find/access AmazingCharts.xml file, after the SBS2011 server upgrade, twice, and we had to change the permissions of the Amazing Charts folder to Everyone. And do it for every subfolder.
Right click the folder>properties>security>edit>add>Everyone
And then give them full control of the folder. Start Amazing Charts and point it to the.xml file folder.
